Math word problem

Question

To mail a small package it costs 54cent for the first ounce an 43 cents for each additional ounce how much more would it cost to mail seven 1ounce packages than to mail one package weighing 7 ounce

Answer 1

mailing 7 packages that each weigh 1 oz. will cost 7(.54) = $3.78

make an equation to calculate the cost of mailing a package that weighs more than 1 oz.

f(x) = .54 + .43(x - 1)

we use x-1 because the first ounce is accounted for by the .54

to mail a package that weighs 7 oz. solve for f(7)

f(7) = .54 + .43(7 - 1) = .54 + .43(6) = .54 + 2.58 = $3.12

so it costs 3.78 - 3.12 = $.66 more